Hepatocellular carcinoma metastatic to the kidney mimicking renal oncocytoma

Renal metastases of hepatocellular carcinoma (HCC) are very rare. To our knowledge only five cases have been reported to the present; all had a well-known primary HCC.

We describe the clinico-pathological features of a rare case of HCC metastatic to the kidney in which the renal mass was the clinical debut of disease. The patient was a 54-year-old woman previously submitted to orthotopic liver transplantation, who underwent left nephrectomy for a renal mass.

Histologically, the tumor was composed mainly of epithelioid cells with homogeneous acidophilic cytoplasm resembling oncocytoma or primary renal carcinoma with oncocytic features. A correct diagnosis was made on the basis of positive immunostaining for hepatocyte paraffin 1.

Metastasis to the kidney is a rare complication that should be considered whenever a renal mass is present in patients with HCC. Since HCC may histologically resemble primary renal tumors such as oncocytoma, pathologists must be aware of this possibility above all in patients referred for liver transplantation and treated with immunosuppressant drugs. Immunohistochemistry is particularly helpful to establish a precise diagnosis in cases of doubt.